Mechanism for control pulsatile fluid flow

ABSTRACT

This application relates to an apparatus for imparting a pulsatile flow to fluid in a conduit, which has pumping means for providing the pulsatile flow of fluid therein. The apparatus includes an elastic tubular section defining a portion of the conduit and located downstream of the pulsatile flow providing means. The tubular section is surrounded by a sealed sleeve to define a pressurizable space about the tubular section. The space is pressurizable so that the pulsatile flow pattern of fluid passing through the tubular section is controlled in a manner responsive to the pressure within said space. If desired, a portion of the flow conduit upstream of the pumping means is of enlarged transverse dimension and sealed within a second sleeve to define a second pressurizable space to provide a means for increasing the flow of fluid into the pulsatile pumping means.

United States Patent 1 1 3,639,084

Goldhaber 1 Feb. 1, 1972 [54] MECHANISM FOR CONTROL OTHER PUBLICATIONSPULSATILE FLUID FLOW [72] Inventor: Richard Paul Goldhaber, Chicago,Ill.

[73) Assignee: Baxter Laboratories, Inc., Morton Groove,

Ill.

[22] Filed: Apr. 6, 1970 [211 App]. No; 25,782

l52| US. Cl ..4l7/394, l28/l,23/258.5, l95/l .7 [511 Int. Cl. ..F04b43/10, F04b 45/00, Afilb lQ/OO, A6lm [58] Field ol'Search l28/l DIG. 3;23/2585; I95/l.7; 417/395, 394, 540. 53, 542

[56] References Cited UNITED STATES PATENTS 2,405,734 8/1946 Coe..4l7/395 3.490.438 l/l970 Lavender et al. ..l28/l R The Lancet-Jan. 25,I958, page I97 By Rotellar Primary Examiner-Robert M. WalkerAttorney-Walter C. Kehm and W. Garrettson Ellis ABSTRACT Thisapplication relates to an apparatus for imparting a pulsatilc flow tofluid in a conduit, which has pumping means for providing the pulsatileflow of fluid therein The apparatus includes an elastic tubular sectiondefining a portion of the conduit and located downstream of thepulsatile flow providing means The tubular section is surrounded by asealed sleeve to define a pressurizable space about the tubular section.The space is pressurizable so that the pulsatile flow pattern of fluidpassing through the tubular section is controlled in a manner responsiveto the pressure within said space. If desired, a portion of the flowconduit upstream of the pumping means is of enlarged transversedimension and sealed within a second sleeve to define a secondpressurizable space to provide a means for increasing the flow of fluidinto the pulsatile pumping means.

6 Claims, 3 Drawing Figures Pmmmm um 3539.084

SHEEI 1 BF 2 [220622 far MECHANISM FOR CONTROL PULSATILE FLUID FLOWBACKGROUND OF THE INVENTION Equipment for providing a pulsatile flow offluid through a conduit is currently used in experimental and clinicalwork relating to organ perfusion and the like. it has been found thatthe life span of surgically removed living organs, such as livers,hearts, or kidneys, can be prolonged by perfusing the organs with anoxygenated solution. In particular, it has been found that the viabilityof such separated organs is prolonged by perfusing them with oxygenatedsolution in a pulsatile flow pattern simulating the beating of theheart.

While several systems for providing a pulsatile flow of oxygenated fluidto living organs have been constructed, deficiencies have been noted inthat the prior art devices are unable to provide a wide variation ofpulsatile flow patterns, so that the user can select the preciseamplitude and shape of the pulsatile flow pressure waves desired. Also,the pumps which provide pulsatile flow do not operate with an optimumvolume of flow.

DESCRIPTION OF THE INVENTION The invention of this application providesa simple means for controlling the pattern of pulsatile flow of fluidthrough a conduit, permitting the alteration of both the amplitude andshape of the pulse or pressure wave as measured against time.Furthermore, this application provides a means for providing increasedvolumes of fluid through a narrow conduit to the pulsatile flow pump forgreater pumping efficiencies.

In accordance with this invention, an apparatus for imparting flow tofluid in a conduit is provided, having pump means for providing apulsatile pressure to cause flow of fluid in said conduit. The apparatuscontains aorta means comprising an elastic tubular section defining aportion of the conduit. The tubular section is located downstream of thepulsatile flow providing means, and is surrounded by a sealed sleeve todefine a pressurizablc space about the section. The space within thesleeve is pressurizable as desired to alter the compliance of thetubular section by controllable pressure to any degree and in anypattern desired. Hence, the pulsatile flow pattern of fluid passingthrough the sleeve having pulsations provided by the pulsatile pumpmeans is modulated in a manner responsive to the pressure within thespace about the sleeve. For example. a constant pressure can be used, oran in phase oscillatory pressure to augment the amplitude and alter theshape of the pulsations, or an out-of-phase oscillatory pressure toreduce, modify, or even eliminate, the pulsations. As a result of this,the ultimate flow pattern is controllable by the selective controllingof the pressure within the space about the tubular section as describedfurther below.

The tubular sections used herein can be of any cross section defining aclosed figure, e.g., round, oval, or the like.

Furthermore, a portion of the fluid flow conduit located directlyupstream of and communicating with the inlet of the pulsatile pump meanscan define an atrium space of enlarged transverse dimension to provide agreater pulsatile flow efficiency, in accordance with the teachings ofAnderson, et al., American Heart Journal, Jan, I967, pages 92-105.

In accordance with this invention, the portion ofthe conduit definingthe atrium space is surrounded by a second sealed sleeve to define asecond pressurizable space about the portion of conduit. The secondspace is pressurized with oscillatory pressure which causes the atriumspace to collapse during the filling phase of the pulsatile pumpingmeans and to expand during the pumping phase of the pulsatile pumpingmeans. Thus, abundant fluid is provided to the pulsatile pumping means,resulting in greater pumping efficiency.

Referring to the drawings:

FIG. I is a schematic view of an organ preservation system in accordancewith this invention.

FIG. 2 is a view, taken in vertical section, of the pulsatile pumpingmeans and related portions used in this invention.

FIG. 3 is a partial vertical sectional view of another embodi ment oftheatrium space and the pulsatile pumping means.

Referring to the drawings, an organ perfusion system is shown in whichperfusate fluid, for example blood or plasma, is pumped through atypically transparent organ preservation chamber 10 to permit viewing ofthe organ. The fluid is driven by a pulsatile pump [2 through conduit 14into chamber 10, through a cannulated organ contained therein, and thenout conduit 16. Access port 17 is provided in organ chamber [0 for useas needed. Port 17 can be connected to the organ to conduct organsecretions out of the chamber [0 to an accumulating container (not shownif desired. The perfusate flow path of the organ preservation system isdisposed in a hyperbaric chamber, if desired, for hyperbaric perfusion.The device can include a compact container for easy transportability.

The liquid perfusate is conducted uniformly from the organ in chamber [0through conduit [6 to a conventional heat exchanger 18, in which thetemperature of the pcrfusate is brought to a desired temperature,generally between 4 and about 37 C. to control the temperature withinthe system. A separate circuit for heat exchanger fluid 20 passes intoclose heat exchanging relation with the perfusate passing into the heatexchanger from conduit l6, but the two fluids are separated by a thinmetal heat transfer partition. Heat exchange fluid such as saline iscirculated in conduits 22 between heat exchanger 18 and a conventionaltemperature control source and pump 24.

Perfusate at a desired temperature passes from heat exchanger 18 viaconduit 26 to a conventional oxygenator 28 (such as described in BelgianPat. No. 726,886) for transferring oxygen to and expelling carbondioxide from the perfusate. Oxygenator 28 also contains an oxygen flowpath com prising line 30 and exhaust line 32. From the oxygenator theperfusate is passed through conduit 34 and sealed connection 36 into anenlarged portion of the conduit which defines atri um space 38,typically made of flexible, limp, thin-walled rubber tubing. Atriumspace 38 provides a flexible storage chamber for perfusate to accumulatebetween filling phases of the pulsatile pump 12, and is surrounded bytubular guard 37.

The amount of perfusate flowing in the system is regulated by addingperfusate as needed from reservoir 4!, controlled by valve 43, tocompensate for liquid lost as secretions through port 17 and the like.

As shown in H0. 2, pulsatile pump 12 comprises a cylinder 42 containingan elastic tube 44 positioned axially within cylinder 42. The space 45between tube 44 and cylinder 42 is sealed by annular seals 47, 49 todefine a sealed annular chamber. lnlet means 46 and outlet means 48 fromthe pump each include a one-way leaf-type flap valve 50, each of whichopens to permit flow into tube 44 through inlet 46 and out outlet 48while preventing backflow of fluid.

Cylinder 42 defines an entrance port 52 to receive fluid from anoscillatory pressure providing system, which includes tube 54 containinga head of hydraulic fluid 56 and which is connected through line 58 to aconventional oscillatory pressure generating control source 60 (FIG. I),operated by gas supply 61, typically oxygen. Control source 60 is shownto provide oscillatory oxygen pressure to line 58, and also to providean oxygen flow to oxygenator 28, typically using oxygen passing througha flowmeter in control source 60. The oscillatory pressure causes fluidto pass back and forth through port 52 to a space 45 within cylinder 42and outside of tube 44 to actuate pump 12 by alternately collapsing tube44 and permitting it to expand again in accordance with the pressure andrelaxation cycles of the oscillatory pressure. As tube 44 collapses,fluid is forced out of outlet means 48 in each pumping phase, and astube 44 expands, fluid passes in through inlet means 46 in each fillingphase. Typically, pump 12 is positioned at a vertically lower positionthan organ chamber [0 to provide a hydrostatic pressure head of fluid toassist in filling of tube 44 during the filling phase. Oxygenator 28 isalso positioned vertically lower than chamber [0 for pressurizationthere.

A suitable pneumatic control source 60 for providing oscillatorypressure to line 58 and entrance port 52 is disclosed in the article byDemers et al., entitled A Perfusion Circuit for Organ Preservation inPortable Chambers." J. Surgical Research, vol. 9, No. 2, pp. 95-99(1969). This article also refers to a suitable combined heatexchangeroxygenator which can be used in substitution for the separatemembers [8 and 28 in this invention. This or other pneumatic systems canbe adjusted to provide the desired period between pulses.

In accordance with this invention, an elastic tubular section 62 definesa portion of the conduit for pulsatile flow of fluid, and is locateddownstream of pulsatile pump 12. Tubular sec' tion 62 is surrounded by asealed sleeve 64, integral with cylinder 42, to define a pressurizablespace 66 between sleeve 64 and tubular section 62. Line 68 leads betweenspace 66 and a pressure control 70 (FIG. I] which connects topressurized oxygen source 6| via line 72.

Pressure control 70 can be a simple constant pressure regulator, or, ifdesired, can be a source of variable pressure, coor' dinated, ifdesired, with the oscillatory pressure provided by source 60. As fluidis forced out of pump 12 in a pulse of pressure, the amplitude and shapeof the pressure wave can be varied by varying the resilience orcompliance of tubular sec tion 62. This resilience, or compliance, iscontrolled as desired by controlling the pressure provided through line68, thus varying the capacity of tubular section 62 to receiveperfusate. If high pressure is provided, the compliance characteristicsof tube 62, when exposed to the pressure wave passing out of pump [2,are quite different from the compliance charac teristics of tube 62 whenthere is a low pressure or a reduced pressure within conduit 68 andspace 66. A constant pressure can be provided within space 66, as wellas an oscillatory pres sure of any type desired, either in phase or outof phase with the oscillatory pressure used to drive pump I2. Thus greatflexibility is available in the control of the shape of the pressurepulse of the oscillatory fluid flow passing through conduit 14 to organchamber I0.

Referring to FIG. 3, there is shown a modification of a device which isotherwise similar to the device of FIGS. I and 2 except as stated. Theportion of conduit defining atrium space 38 and disposed within guard orsleeve 37 is sealed by cap 70 to define another pressurizable space 72.The conduit defining atrium chamber 38 is typically glued to cap 70 at74 to make the space fluidtight. Line 76 leads between space 72 and asource of oscillatory pressure such as source 60. The pressureoscillations in spaces 45 and 72 are arranged to be out of phase witheach other, generally with the pulses in space 72 shortly preceding thepulses in space 45. Hence, as elastic tube 44 of pump I2 is in thefilling phase of its pumping cycle for receiving fluid through inlet 46,line 76 is providing a pulse of pressure to space 72 to collapse theconduit defining atrium space 38 to force fluid into pump I2. No checkvalve is needed to prevent excessive backflow of fluid from atrium space38. The majority of fluid in atrium space 38 passes into pump I2 withoutsuch a valve because inlet 46 is wider than conduit 34 and because thepressure in conduit 34 caused by the elevated organ chamber is greaterthan the pressure within tube 44 during the filling cycle, because oftheinherent resiliency of the tube and its tendency to spring back to itsuncollapsed position, For greater efficiency, a check valve can beprovided, ifdesired.

Out of phase oscillatory pressure is provided to space 45 through line78 and port 79 by a conventional time delay device connected to line 76to operate a pilot valve in line 78 which opens the line in one positionand closes, but permits backward venting, in another position, toprovide oscillatory pressure in tube 80 and space 45. Line 78 is thenconnected to a pressure source such as oxygen supply 61, to provide aconstant pressure to line 78 upstream ofthe pilot valve A typical timedelay device can constitute a conduit c0n nectcd to line 76, runningthrough a chamber of predetermined volume, and then past an adjustableneedle valve to a pressure responsive switching control of the pilotvalve. The

size of the chamber and the needle valve are adjusted to give I thedesired time delay A suitable pilot valve is available from theFluidonics Division of Imperial Eastman Corporation of Chicago, Illinoisunder the part number 3001 35.

During the pumping phase of pump I2 in FIG. 3, flap valve 50 of inlet 46is closed, and the oscillatory pressure in space 72 and line 76 is at areduced level to permit the conduit which defines atrium chamber 38 tofill once again with perfusate.

The pressure pattern in space 72 can be arranged so that the duration ofeach pressure pulse with collapses the portion of conduit definingatrium space 38 lasts for only a portion of the filling phase oftube 44.

In a specific embodiment, the oscillatory pressure in line 76 has amaximum pressure of about 20 mm. Hg, while the oscillatory pressureprovided to lines 58 or 78 and from thence to pump [2 has a maximumpressure of about IOU mm. Hg. The frequency of oscillation for bothoscillatory pressures is, for example, 60 cycles per minute. Thepressure provided in line 68 can be constant at 20 mm, Hg. A constantpressure of this level in line 68 assures that a minimum bias diastolicpressure is constantly present in the system between pulsations of flow,and particularly that such minimum bias pressure is imposed upon theorgan within chamber I0 through line l4. It is believed that thisprolongs organ viability.

The parts which contact the perfusate are typically made of siliconerubber to be atraumatic to blood.

The apparatus of this invention can use any fluid in conduit 68 and thespace between tubular section 62 and sleeve 64, and in the otherpressurizable areas, depending upon the com pliance characteristicsdesired. Liquids of varying viscosity such as oil, silicone fluid, orwater, provide differing compliance characteristics, which in turndiffer from the compliance characteristics of gases. An incompressibleliquid such as saline can be used, while closing off conduit 68, toprovide very little compliance to tubular section 62, in which there isvery little damping or modulation of the pressure pulses passingtherethrough.

The above specific disclosure is for illustrative purposes only and isnot for purposes of limiting the scope of the invention of thisapplication. Broadly, the invention of this applica tion can be utilizedin many different devices, including organ perfusion apparatuscomprising (a) container means for receiving an organ; (b) means fordelivering perfusate to the organ within the container, (c) means fordeveloping pulsatile pressure in the perfusate delivered to the organ;(0') means for imposing a minimum pressure bias on perfusate circulatedthrough the organ between pressure pulses; (e) means for oxygenatingperfusate conducted from the organ; and (1') control means fordetermining the pump output, the control means comprising means forsetting the period of each high pressure pulse.

Manual control means can be provided to vary the temperatu re andpressure of perfusate provided to the organ, as well as for regulatingthe pulse rate and systole period of each pulse developed by the pumpmeans.

That which is claimed is:

l In an organ perfusion apparatus for passing fluid in a conduit throughan organ in a container including pump means for providing a pulsatilepressure to cause flow of fluid in said conduit, in which said pumpmeans comprises a cylinder con taining an elastic tube positionedaxially therein, means for sealing the interior of said tube from theexterior thereof to define a sealed flow path for fluid to be pumped,and inlet and outlet means to allow said fluid to pass through the tube,said inlet and outlet means each containing a one-way valve to preventbackflow of fluid, said cylinder defining an entrance port to receivefluid within the cylinder and outside said tube from first oscillatorypressure providing means, to actuate said pulsatile pressure providingmeans by repeatedly collapsing said tube and permitting it to expandagain by application of oscillatory pressure, in which a portion of saidconduit defines an atrium space of enlarged transverse dimension, saidatrium space being located directly upstream of and extending to saidinlet means of the pump means, in which said atrium space is surroundedby a second sealed sleeve to define a second pres surizable space aboutsaid portion of conduit, and in which said second sleeve has secondmeans for pressurizing said second space with oscillatory pressure whichis out of phase from the oscillatory pressure provided by said firstoscillatory pressure providing means, so that when the elastic tube ofthe pump means is in its filling phase. the portion of conduit definingsaid atrium space is in its collapsing phase to provide pressurizedfluid to said inlet means. for greater pumping efficien- 2. The organperfusion apparatus of claim 1 in which an elastic tubular sectiondefines a portion of said conduit and is located between said pump meansand said organ container. the elastic tubular section being surroundedby a sealed sleeve to define a pressurizable space about said tubularsection, and

means for controlling the pressure in said space. whereby the pulsatileflow pattern of fluid passing through said tubular section is controlledin a manner responsive to the pressure within said space.

3. The apparatus of claim 2 in which said elastic tubular section ispositioned downstream of and adjacent to said pulsatile pressureproviding means.

4. The apparatus of claim 2 in which said conduit for pulsatile fluidflow defines a closed loop circuit.

5. The apparatus of claim 2 in which said sealed sleeve and saidcylinder define a single. integral member.

6. An organ perfusion device incorporating the apparatus defined inclaim 2.

1. In an organ perfusion apparatus for passing fluid in a conduitthrough an organ in a container including pump means for providing apulsatile pressure to cause flow of fluid in said conduit, in which saidpump means comprises a cylinder containing an elastic tube positionedaxially therein, means for sealing the interior of said tube from theexterior thereof to define a sealed flow path for fluid to be pumped,and inlet and outlet means to allow said fluid to pass through the tube,said inlet and outlet means each containing a one-way valve to preventbackflow of fluid, said cylinder defining an entrance port to receivefluid within the cylinder and outside said tube from first oscillatorypressure providing means, to actuate said pulsatile pressure providingmeans by repeatedly collapsing said tube and permitting it to expandagain by application of oscillatory pressure, in which a portion of saidconduit defines an atrium space of enlarged transverse dimension, saidatrium space being located directly upstream of and extending to saidinlet means of the pump means, in which said atrium space is surroundedby a second sealed sleeve to define a second pressurizable space aboutsaid portion of conduit, and in which said second sleeve has secondmeans for pressurizing said second space with oscillatory pressure whichis out of phase from the oscillatory pressure provided by said firstoscillatory pressure providing means, so that when the elastic tube ofthe pump means is in its filling phase, the portion of conduit definingsaid atrium space is in its collapsing phase to provide pressurizedfluid to said inlet means, for greater pumping efficiency.
 2. The organperfusion apparatus of claim 1 in which an elastic tubular sectiondefines a portion of said conduit and is located between said pump meansand said organ container, the elastic tubular section being surroundedby a sealed sleeve to define a pressurizable space about said tubularsection, and means for controlling the pressure in said space, wherebythe pulsatile flow pattern of fluid passing through said tubular sectionis controlled in a manner responsive to the pressure within said space.3. The apparatus of claim 2 in which said elastic tubular section ispositioned downstream of and adjacent to said pulsatile pressureproviding means.
 4. The apparatus of claim 2 in which said conduit forpulsatile fluid flow defines a closed loop cIrcuit.
 5. The apparatus ofclaim 2 in which said sealed sleeve and said cylinder define a single,integral member.
 6. An organ perfusion device incorporating theapparatus defined in claim 2.